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Disinfection with Chlorine & Chloramine

Water can come from a variety of sources, such as lakes and wells, which can be contaminated with germs that can make people sick. Germs can also contaminate water as it travels through miles of piping to get to a community. To prevent contamination with germs, water companies add a disinfectant—usually either chlorine or chloramine1—that kills disease-causing germs such as Salmonella, Campylobacter, and norovirus. The type of chloramine discussed on this page that is used to treat drinking water (monochloramine) is not the same type that can form and harm the indoor air quality around swimming pools (dichloramine or trichloramine) 2.

Chlorine was first used as a drinking water disinfectant in Europe in the late 1800s. It was first used in the U.S. in 1908 in Jersey City, New Jersey 1. Chloramine has been used as a drinking water disinfectant in the U.S. in places like Cleveland, Ohio, Springfield, Illinois, and Lansing, Michigan since 1929 2. Today, chlorine and chloramine are the major disinfectants used to disinfect public water systems.

How can I find out what's in my drinking water?

Many public water systems have to add a disinfectant to the water. The disinfectant must be present in all water found in the pipes that carry the water throughout the community 3. Most communities use either chlorine or chloramines. Some communities switch back and forth between chlorine and chloramines at different times of the year or for other operational reasons 4. Less commonly, utilities use other disinfectants, such as chlorine dioxide 2. Some water systems that use water from a groundwater source (like community wells) do not have to add a disinfectant at all 5. You can find out whether there is a disinfectant in your water, what kind of disinfectant is used, and how well your utility has remained in compliance with the rules about disinfection by obtaining a copy of your utility's consumer confidence report3. This is an annual report that your utility has to send to all customers every year.